Objective:To study the effects of IL-8 on the polarization of monocytes and the effects of IL-8-induced tumor-associated macrophages(TAMs)on the invasion and metastasis of hepatocellular carcinoma(HCC).Methods:After exogenous IL-8 stimulation of THP-1 cells for 72h,the percentages of M1 and M2 TAMs were examined.RT-PCR and Western blot assays were used to study epitheli-al-mesenchymal transition(EMT),and wound-healing and transwell assays were preformed to study the invasion potential of HCC cells after co-culturing with TAMs and HCC cell lines in vitro.Lastly,100 cases of HCC tissue samples were used to validate the correlation among TAM numbers,IL-8,and EMT features of HCC cells via immunohistochemistry(IHC)staining methods.Results:Exogenous IL-8 induced significant M2 polarization of TAMs in THP-1 cells.TAMs further promoted EMT in HCC and enhanced the invasion potential of HCC in vitro.Finally,significant positive correlations among the numbers of TAMs,IL-8 expression,and N-cadherin expression were identified in primary HCC tissue samples(r=0.22,r=0.20,P<0.05).Conclusions:IL-8 locally attracted and activated TAMs,and promot-ed M2 polarization of TAMs,which further promoted the EMT and invasion potential of HCC cells both in vitro and in vivo.